In logic circuits, a flip-flop is a term referring to an electronic circuit that has two stable states and thereby is capable of serving as one bit of memory. A flip-flop is usually controlled by one or two control signals and/or a gate or clock signal. The output often includes the complement as well as the normal output. Flip-flops can be either simple (transparent) or clocked (or non-transparent). Clocked flip-flops are specially designed for synchronous (time-discrete) systems and typically implemented as master-slave devices. Flip-flops can be further divided into types: the RS (“set-reset”), D (“data” or “delay”), T (“toggle”), and JK types are the common ones. The D flip-flop is known as delay flip-flop (as its output Q looks like a delay of input D) or data latch. The behavior of a particular type flip-flop can be described by what is termed the characteristic equation, which derives the “present state” output in terms of the input signal(s) and/or the “previous state” signal of the flip-flops.
The metal-oxide-semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a device used for amplifying or switching electronic signals. It is made of a solid piece of semiconductor material. The four terminals of the MOS FET are named source, gate, drain, and body (substrate). In MOSFETs, a voltage on the oxide-insulated gate electrode can induce a conducting channel between the two other contacts called source and drain, when the transistor is turned ON. The channel can be of n-type or p-type, and is accordingly called an nMOSFET or a pMOSFET (also commonly nMOS, pMOS). When there is no conducting channel between the source and the drain, when the transistor is turned OFF, the source and the drain will maintain their voltage levels. The detailed operations of nMOS and pMOS transistors are known to those of skill in the art.
A signal is a digital signal that can have value 0 (LOW voltage) or 1 (HIGH voltage). Logic value 0 and LOW voltage will be used interchangeably for illustration purpose only. The embodiments may well function if the correspondence of voltage level and logic value is changed. For any signal x, the notion xb refers to the complement or inverted signal of x. For a signal x, its complement signal or inverted signal xb has value 0 if x has value 1, and xb has value 1 if x has value 0.
The drawings, schematics and diagrams are illustrative and not intended to be limiting, but are examples of embodiments of the invention, are simplified for explanatory purposes, and are not drawn to scale.